1. Field of the Invention
The invention relates to an image processing device, an image processing method, a program for executing image processing, and a computer readable recording medium on which the program is stored. In particular, the invention relates to an image processing device, an image processing method, a program for executing image processing, and a computer readable recording medium on which the program is stored that execute area separations for separating photographic areas, graphic areas and character areas from image data to be processed.
2. Description of the Related Art
Image processing technology has been known for identifying photographic areas, graphic areas, and character areas from image data obtained by scanning an original document, applying an appropriate image process to each, and then synthesizing the areas to produce output image data (e.g., Unexamined Publication No. JP-A-5-342408).
However, it is sometimes difficult to identify accurately the type of each area contained in the image data using the conventional art. For example, there is a great risk of making misjudgments in identifying areas when multiple types of areas are laid out in a complex manner or overlapping with each other in image data.
For example, if a graphic area is laid out in a photographic area overlapping with each other, there is a risk of overlooking the graphic area and extracting the entire area misjudging it as a photographic area. Therefore, if a compression process appropriate to photographic areas, such as the JPEG compression process, is applied to such an extracted area, the graphic area located in the photographic area may get compressed by the JPEG compression and may cause noises such as edge blurring. As a result, it may deteriorate a graphic image located in the photographic area. Also, since graphic images and character images share a common characteristic that both consist of line segments, a graphic area can be misjudged to be a character area and can be applied with a character recognition process.
As can be seen from the above, there was always a risk of not being able to extract graphic areas from the image data without fail even when it is desired to extract them concentrating on graphic areas that contain graphics images and apply processes that are suitable for graphic areas such as a vector transformation process, consequently ending up causing image deteriorations as a result of applying inappropriate processes to the graphic areas.
Moreover, if there is a part that is misjudged as a character area in a photographic area, there is a possibility of applying a binary process applicable to character areas by mistake to the part. Moreover, if there is a part that is misjudged as a graphic area in a photographic area, it can be painted by mistake with a single color in the downstream process as a result of a color reduction process that is applicable to graphic areas. Consequently, the picture quality of the photographic image can result in severe degradation.
As can be seen from the above, there was always a risk of not being able to extract photographic areas from the image data without fail even when it is desired to extract them concentrating on photographic areas that contain photographic images and reproduce the extracted photographic areas with a high image quality, consequently ending up causing image deterioration as a result of applying inappropriate processes to the photographic areas.
Moreover, if there exists a character image overlapping a photographic image or a graphic image in image data, there is a risk of overlooking the character area and extracting the entire area recognizing it as a photographic area or a graphic area. Also, if a compression process appropriate to photographic areas, such as the JPEG compression process, is applied to such an extracted area containing character images, the character images located in the photographic area may get deteriorated and may become illegible images when reproduced.
As can be seen from the above, there was always a risk of not being able to extract character areas without fail when it is desired to extract them concentrating on character areas that contain character images from image data and execute processes appropriate for character areas such as the character recognition process, consequently ending up not only being unable to perform character recognition processes sufficiently on the character images but also causing inappropriate processes to the character images.
On the other hand, depending on the contents of the original document, the user may want to apply processes appropriate to graphic areas such as a vector transformation to graphic areas as the graphic areas of the image data are important, or may want to reproduce photographic areas as the photographic areas are important, or may want to perform character recognition processes to character images in other areas as the character areas are important. In other words, it is desirable to be able to perform any processes on the image data depending on the contents of the original document.